JP5945723B2 - rice cooker - Google Patents

Description

  The present invention relates to a rice cooker used in a general household.

  Conventionally, this type of rice cooker has a heating coil for heating a pan, inverter means for supplying a high-frequency current to the heating coil, switching means constituting the inverter means, and a peak for detecting a voltage across the switching means. The voltage detection means and the input current detection means for detecting the input current supplied to the rice cooker from the AC power source, the higher of the output of the peak voltage detection means and the output of the input current detection means Depending on the output, the on-time of the switching means is shortened to control the input current (see, for example, Patent Documents 1 and 2).

  Also, there is provided a coil current detecting means for detecting a current flowing in the heating coil, and controlling an input current supplied from an AC power source according to the output of the coil current detecting means and the output of the input current detecting means. Yes (see, for example, Patent Document 3).

  FIG. 6 shows a system diagram of a conventional rice cooker described in Patent Document 1. As shown in FIG. As shown in FIG. 6, an AC power source 35, a current transformer 44 constituting the input current detecting means 43, a switching means 34 constituted by an IGBT, an emitter follower circuit for detecting a peak value of the collector voltage of the IGBT, etc. And a control means 52 comprising a microcomputer for controlling the on-time of the switching means 34 in accordance with the output values of the input current sensing means 43 and the peak voltage sensing means 51. ing.

  It also has an overvoltage detection circuit that detects whether the voltage of the AC power supply is larger or smaller than the value at which the inverter circuit operates normally, and controls the operation of the inverter to stop when it is determined that the voltage is high. There are some (see, for example, Patent Document 4).

  In addition, there is also a device that includes voltage detection means for detecting the voltage of the commercial power supply and controls the operation of the inverter to be stopped when the detected voltage is equal to or lower than a certain voltage (see, for example, Patent Document 5).

  There is also a power supply abnormality detection circuit that monitors the power supply voltage and detects an abnormal voltage of the power supply voltage, and controls to stop the operation of the inverter when a power supply abnormality is detected (for example, Patent Document 6). reference).

Japanese Examined Patent Publication No. 61-26306 Japanese Patent Laid-Open No. 5-114472 JP 2003-135272 A Japanese Patent Laid-Open No. 5-114473 JP 2007-289304 A Japanese Patent Publication No. 4-71318

  However, in the conventional configuration, since the ON time of the switching means is set so that the input current is constant, when the voltage of the AC power supply decreases, the input current is constant at that voltage. The AC power supply voltage is set to be longer than the ON time in the state of operating at the rated voltage. In this state, when the AC power supply voltage returns to the rated voltage, the on-time setting means operates at the instant when the AC power supply voltage is restored while the on-time setting means is set at the on-time when the AC power supply voltage is reduced.

  Therefore, when the rated voltage is restored, the time until the output value of the input current detecting means and the output value of the input current setting means become the same is equal to or greater than the input current set by the current setting means, and the switching means Because the resonance voltage applied to the switching means is increased because the on-time of the is increased, a voltage higher than the rated voltage of the switching means is applied, or the electrons used inside the rice cooker Exceeding the rated current value of a component or a semiconductor component has caused the problem that the component is broken or deteriorated, and the life is shortened.

  In addition, assuming that an abnormality occurs in the AC power supply, it is necessary to provide a detection circuit for detecting the voltage of the AC power supply and a power supply abnormality detection circuit for detecting the abnormal voltage of the AC power supply voltage, which increases the number of parts. It had the problem that.

The present invention solves the above-described conventional problems, and does not require a detection circuit for detecting the voltage of the AC power supply or a power supply abnormality detection circuit for detecting an abnormal voltage of the AC power supply voltage, and the abnormality of the AC power supply voltage. The purpose is to provide a rice cooker that can detect a drop and protect the components when the voltage is restored .

In order to solve the conventional problems, the rice cooker of the present invention detects an input current supplied from an inverter means for supplying high-frequency power to a heating coil, a switching means constituting the inverter means, and an AC power supply. An input current detecting means, an input current setting means for setting a target value of the input current, an on time setting means for setting an on time of the switching means, and a maximum value of a change amount of the on time in a fixed time. Maximum on-time change amount setting means, and control means for controlling the on-time of the on-time setting means and the energization operation of the switching means according to the output value of the input current detection means and the output value of the input current setting means And the control means is configured such that a change amount of the on-time set by the on-time setting means in a certain time is the maximum on-time change amount setting. At the set-on hours of variation of the stage, in which so as to stop the power supply operation of said switching means.

  As a result, when the AC power supply voltage decreases, the on-time set by the on-time setting unit of the switching unit increases, so that the amount of change of the set on-time in a certain time is the set on-time of the maximum on-time variation setting unit When the above-mentioned on-time is reached, the control means determines that the voltage of the AC power supply has instantaneously dropped to a voltage value below a certain value, and the energization operation of the switching means is stopped, so detection for detecting the voltage of the AC power supply A circuit or a power supply abnormality detection circuit that detects an abnormal voltage of the AC power supply voltage is not required, and an instantaneous abnormality drop of the AC power supply voltage can be detected to protect the components when the voltage is restored.

  The rice cooker of the present invention determines that the voltage of the AC power supply is low based on the ON time set by the ON time setting means of the switching means, and the AC power supply voltage returns to normal by stopping the energization operation of the switching means. In this case, it is possible to prevent the electronic components and semiconductor components used in the rice cooker from being destroyed, deteriorated, or shortened in life.

Main part system block diagram of rice cooker in Embodiment 1 of this invention Operation timing chart of main part of rice cooker in embodiment 1 of the present invention The graph which shows the relationship between the ON time of the switching means of the rice cooker in Embodiment 1 of this invention, and input current Main part system diagram of rice cooker in embodiment 2 of the present invention The graph which shows the relationship between the ON time of the switching means and input current in Embodiment 2 of this invention System diagram of conventional rice cooker

The first invention is a heating coil for heating a pan, inverter means for supplying high-frequency power to the heating coil, switching means for constituting the inverter means, rectification for rectifying an AC power source and supplying power to the inverter means Means, input current detection means for detecting an input current supplied from the AC power supply, input current setting means for setting a target value of the input current, and on time setting means for setting an on time of the switching means. A maximum on-time change amount setting means for setting a maximum value of a change amount of the on-time in a fixed time, and the on-time setting means according to the output value of the input current detection means and the output value of the input current setting means And an ON time set by the ON time setting means. When the amount of change in the fixed time period is set ON hours of the variation of the maximum on-time change amount setting means is for stopping the power supply operation of said switching means.

  As a result, when the voltage of the AC power supply decreases, the on-time set by the on-time setting unit of the switching unit becomes large. When the on-time longer than the time is reached, the control means determines that the AC power supply voltage has instantaneously dropped to a voltage value below a certain value, and the energization operation of the switching means is stopped, so detection for detecting the voltage of the AC power supply When the AC power supply voltage returns to normal without detecting a circuit or a power supply abnormality detection circuit that detects an abnormal voltage of the AC power supply voltage, the AC power supply voltage returns to normal. It is possible to prevent the used electronic parts and semiconductor parts from being destroyed, deteriorated, and shortened in life.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a system configuration diagram of a main part of a rice cooker according to the first embodiment of the present invention.

  In FIG. 1, a pan 1 is magnetically coupled to a heating coil 2 that is a heating means. The resonance capacitor 3 is connected in parallel to the heating coil 2 and constitutes a parallel resonance circuit with the heating coil 2.

  The switching element 4 which is a switching means is composed of a semiconductor element such as a MOSFET or IGBT and a reverse connection diode which is reversely connected to the semiconductor element. In the present embodiment, an inverter circuit 5 which is an inverter means for supplying a high-frequency current to the heating coil 2 is composed of a resonance capacitor 3 and a switching element 4.

  The rectifying means 6 includes a diode bridge 7 that is a rectifying element, a choke coil 8, and a high-frequency smoothing capacitor 9, which rectifies and smoothes an AC power supply 10 and supplies a substantially DC voltage to the inverter circuit 5.

  The choke coil 8 prevents the high-frequency current component of the inverter circuit 5 from leaking as high-frequency noise to the AC power supply 10 side.

  The input current detection means 11 is composed of a current transformer 12, a resistor 13, a diode bridge 14, and an electrolytic capacitor 15, and an AC output signal of the current transformer 12 connected between the AC power supply 10 and the rectification means 6 is a diode bridge. 14 is converted into a DC signal by a rectifying / smoothing circuit constituted by an electrolytic capacitor 15.

  The resistor 13 is for adjusting the output voltage value of the current transformer 12. The input current detection means 11 can detect the input current Iin supplied from the AC power supply 10.

  The driving means 16 is composed of a push-pull circuit using an NPN transistor and a PNP transistor, and a high voltage is applied to the IGBT constituting the switching element 4 when the PWM circuit 18 in the microcomputer 17 outputs a high pulse. Is output.

  While the high voltage is applied to the switching element 4, the switching element 4 is in a conductive state, and the energy charged in the high frequency smoothing capacitor 9 is supplied to the heating coil 2 as a high frequency current.

  The microcomputer 17 stores in advance an 8-bit set value corresponding to a target value of a plurality of input currents Iin in an internal ROM, and corresponds to a predetermined target value for each condition such as the rice cooking process and the size of the pan. The input current setting means 19 for outputting the set value of 8 bits, the on time setting means 20 for setting the switching on time of the switching element 4, and the output voltage of the input current detection means 11 are input to the AD converter, The control means 21 for controlling the ON time of the switching means set by the ON time setting means 20 by comparing the input value and the output value of the input current setting means 19, and the ON time set by the ON time setting means 20 is output as a high pulse. The maximum value of the set on-time of the PWM circuit 18 that performs the on-time setting unit 20 that sets the on-time of the switching element 4 that is the switching unit. And a maximum on-time setting means 22 for.

When the ON time set by the ON time setting means 20 is set to be equal to or longer than the ON time set by the maximum ON time setting means 22, the control means 21 prohibits the PWM circuit 18 from outputting a high pulse and performs switching. The switching energization operation of the element 4 is stopped.

  The synchronizing signal output means 23 includes a first resistance voltage dividing circuit 24 that detects the collector voltage of the IGBT of the switching element 4 that is a switching means, and a second resistance voltage dividing circuit that detects the output voltage of the rectifying means 6. 25, and a comparison circuit 26 that compares the outputs of the first resistance voltage dividing circuit 24 and the second resistance voltage dividing circuit 25.

  The comparison circuit 26 is composed of a comparator, and outputs low when the output of the first resistance voltage dividing circuit 24 is larger than the output of the second resistance voltage dividing circuit 25, and the output of the first resistance voltage dividing circuit 24. Is smaller than the output of the second resistance voltage dividing circuit 25, it outputs high.

  The output of the synchronizing signal output means 23 is input to the PWM circuit 18. The PWM circuit 18 detects that the output signal is switched from a low output to a high output, and outputs a high pulse. The voltage dividing ratio of the first resistance voltage dividing circuit 24 and the voltage dividing ratio of the second resistance voltage dividing circuit 25 are different. This is to optimize the switching timing of the switching element 4.

  About the rice cooker comprised as mentioned above, the operation | movement and an effect | action are demonstrated below, referring FIG.2 and FIG.3.

  FIG. 2 is an operation timing chart showing the relationship between the voltage and current during the operation of the switching element 4 and each component of the rice cooker in the first embodiment of the present invention.

  2A is a collector voltage (Vce) of the switching element 4 (IGBT) constituting the switching means, FIG. 2B is a current (Ic) of the switching element 4 (IGBT), and FIG. 2 (d) shows the output voltage (Vin2) of the second resistor voltage divider circuit 25, FIG. 2 (e) shows the output voltage of the comparator circuit 26, and FIG. f) shows the output of the PWM circuit 18.

When the PWM circuit 18 outputs a high signal as shown in FIG. 2 (f), the switching element 4 is turned on via the driving means 16, and a current flows through the heating coil 2. At this time, the current (Ic) flowing through the switching element 4 rises with time as shown in FIG. The time variation dI / dt of the current flowing through the switching element 4 is expressed as follows: the voltage _VL applied to the heating coil 2 and the inductance of the heating coil are L.
[Formula 1] dI / dt = V _L / L
It becomes.

  When the ON time reaches the ON time (Ton) set by the ON time setting means 20, the PWM circuit 18 outputs a low signal, and the switching element 4 is turned OFF via the driving means 16.

  As a result, the current flowing through the heating coil 2 flows through the resonant capacitor 3 and the collector voltage (Vce) of the switching element 4 (IGBT) increases as shown in FIG.

  The output voltage (Vce2) of the first resistance voltage dividing circuit 24 shows a waveform proportional to the collector voltage (Vce) of the switching element 4 as shown in FIG.

  When the collector voltage (Vce) of the switching element 4 increases, the output voltage (Vce2) of the first resistance voltage dividing circuit 24 becomes higher than the output voltage (Vin2) of the second resistance voltage dividing circuit 25, and FIG. ), The output of the comparison circuit 26 becomes low.

  Thereafter, the collector voltage (Vce) of the switching element 4 decreases due to the resonance of the heating coil 2 and the resonant capacitor 3, and the output voltage (Vce2) of the first resistance voltage dividing circuit 24 becomes the output of the second resistance voltage dividing circuit 25. It becomes smaller than the voltage (Vin2), and the output of the comparison circuit 26 becomes high. As shown in FIG. 2F, the PWM circuit 18 receives the high output of the comparison circuit 26 and outputs a high signal again.

  By repeating this operation, the switching element 4 can be switched at high speed, and high frequency power can be supplied to the heating coil 2. When the ON time of the switching element 4 is increased, the current (Ic) of the switching element 4 and the heating coil 2 increases, and high-frequency power, that is, input current Iin increases. At the same time, the collector voltage (Vce) of the switching element 4 also increases.

  FIG. 3 is a graph showing the relationship between the ON time of the switching means and the input current in the first embodiment of the present invention, which is set by the input current Iin supplied from the AC power supply 10 and the ON time setting means 20. It is a graph which shows the relationship of on time (Ton).

  When the power supply voltage Vin of the AC power supply 10 is a constant voltage (for example, Vin = 100V), the input current Iin indicates that the input current Iin increases as the on-time (Ton) set by the on-time setting unit 20 increases. ing.

  Specifically, in order to supply 12 A of the input current Iin at the AC power supply voltage Vin = 100 V, the on time requires Ton1 (point a), and when the on time extends to Ton2, the input current Iin is 14 A ( Ascend to point b).

  Further, when the AC power supply voltage (Vin) is low, the input power (Iin) is low in the same on-time (Ton). Specifically, at the AC power supply voltage Vin = 80V, the input current (Iin) is Iin at the on time Ton1 (point a) required to supply the input current Iin of 12A with the AC power supply voltage Vin = 100V. = 10 A (point c).

  That is, in order to supply the input current (Iin) up to 12 A at the AC power supply voltage Vin = 80 V, it is necessary to extend the on-time (Ton) to Ton2 (point d).

  Here, the relationship between the on time (Ton) and the input current (Iin) when the AC power supply 10 drops from the rated voltage 100V to 80V due to a power supply abnormality and then returns to the rated voltage will be described.

  On-time setting when the target value of the input current setting means 19 is set so that the AC power supply voltage (Vin) is 100V, the rice cooker starts the rice cooking operation, and the input current (Iin) is 12A. The means 20 sets the on-time (Ton) to Ton1 (point a) and outputs the on-time to the PWM circuit 18. During the on-time Ton1, the driving means 16 causes the switching element 4 as the switching means to be switched. Energize.

  In this state, when the AC power supply voltage (Vin) decreases to 80 V, the switching element 4 is energized at the on-time Ton1 at the time of the decrease, so the input current (Iin) decreases to 10 A (point c).

The control means 21 detects that the input power (Iin) is lower than 12A by the output from the input current detection means 11, and the on-time of the on-time setting means 20 so that the input power (Iin) is 12A. In order to vary (Ton), the on-time is extended to Ton2 (point d).

  Thereafter, the switching element 4 is energized by the driving means 16 at this on time Ton2 (point d), and the input current (Iin) is operated at 12A.

  In this state, when the AC power supply voltage (Vin) returns to the original rated voltage of 100 V, the switching current 4 is energized at the on-time Ton2 at the instant when the AC power supply voltage (Vin) is restored. To rise.

  At this time, the current (Ic) and the collector voltage (Vce) are applied to the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5 so that the input current (Iin) becomes 14A.

  The control means 21 detects that the input power (Iin) has risen above 12A from the output from the input current detection means 11, and the on-time of the on-time setting means 20 so that the input power (Iin) becomes 12A. In order to vary (Ton), the ON time is shortened to Ton1 (point a).

  Thereafter, the switching element 4 is energized by the driving means 16 at the on time Ton1 (point a), and the input current (Iin) is operated at 12A.

  As described above, when the AC power supply 10 has a power supply abnormality and the AC power supply voltage (Vin) drops from the rated voltage 100 V to 80 V and then returns to the rated voltage, the input current Iin is set by the input current setting means 19. With respect to the target value 12A, it rises to 14A although it is instantaneous at the time of return.

  In this state, components such as the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5, the diode bridge 7 constituting the rectifying means 6, the choke coil 8, and the high frequency smoothing capacitor 9 are allowed to have an allowable current (for example, Ic ) And withstand voltage (for example, collector voltage Vce).

  On the other hand, the relationship between the on time (Ton) and the input current (Iin) when the AC power supply 10 drops from the rated voltage 100V to 70V due to a power supply abnormality and then returns to the rated voltage will be described.

  On-time setting when the target value of the input current setting means 19 is set so that the AC power supply voltage (Vin) is 100V, the rice cooker starts the rice cooking operation, and the input current (Iin) is 12A. The means 20 sets the on time (Ton) to Ton1 (point a), outputs the on time to the PWM circuit 18, and energizes the switching element 4 by the driving means 16 during the on time Ton1.

  In this state, when the AC power supply voltage (Vin) decreases to 70 V, the switching element 4 is energized at the on-time Ton1 at the time of the decrease, and thus the input current (Iin) decreases to 9 A (point e).

  The control means 21 detects that the input power (Iin) is lower than 12A by the output from the input current detection means 11, and the on-time of the on-time setting means 20 so that the input power (Iin) is 12A. In order to vary (Ton), the on-time is extended to Ton3 (point f).

  Thereafter, the switching means 4 is energized by the driving means 16 at this on time Ton3 (point f), and the input current (Iin) is operated at 12A.

  In this state, when the AC power supply voltage (Vin) returns to the original rated voltage of 100 V, the switching element 4 is energized at the on-time Ton3 at the instant when the AC power supply voltage (Vin) is restored. ).

  At this time, the current (Ic) and the collector voltage (Vce) are applied to the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5 so that the input current (Iin) becomes 15.5A.

  The control means 21 detects that the input power (Iin) has risen above 12A from the output from the input current detection means 11, and the on-time of the on-time setting means 20 so that the input power (Iin) becomes 12A. In order to vary (Ton), the ON time is shortened to Ton1 (point a). Thereafter, the switching element 4 is energized by the driving means 16 at the on time Ton1 (point a), and the input current (Iin) is operated at 12A.

  As described above, when the AC power supply 10 has a power supply abnormality and the AC power supply voltage (Vin) decreases from the rated voltage 100 V to 70 V and then returns to the rated voltage, the input current Iin is set by the input current setting means 19. The target value 12A increases to 15.5A although it is instantaneous at the time of return.

  In this state, components such as the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5, the diode bridge 7 constituting the rectifying means 6, the choke coil 8, and the high frequency smoothing capacitor 9 are allowed to have an allowable current (for example, Ic ) And withstand voltage (for example, collector voltage Vce) cannot be designed.

  Specifically, when the collector voltage (Vce) withstand voltage guarantee of the switching element 4 is 1000 V, the AC power supply voltage (Vin) of the AC power supply 10 is turned on in order to pass the input current (Iin) of 12 A when the rated voltage is 100 V. When the on time (Ton) of the time setting means 20 is Ton1 and the switching element 4 is switched, when the collector voltage (Vce) is applied at 750 V, the on time (Ton) of the on time setting means 20 extends to Ton2 and the input current When (Iin) flows through 14 A, a collector voltage (Vce) of 950 V is applied.

  Further, when the ON time (Ton) of the ON time setting means 20 extends to Ton3 and the input current (Iin) flows 15.5 A, the collector voltage (Vce) is applied at 1000 V, and the collector voltage (Vce) withstand voltage guarantee is achieved. It becomes the limit action of.

  That is, when the on-time (Ton) set by the on-time setting means 20 is increased to Ton3, it indicates that the switching element 4 may be destroyed. Therefore, at the Ton time (Ton3), the switching element 4 must not be switched.

  Therefore, the ON time set in the maximum ON time setting means 22 is set to Ton2, which is a value smaller than the above ON time Ton3, and the control means 21 sets the ON time (Ton) set by the ON time setting means 20. However, when the ON time Ton2 set in the maximum ON time setting means 22 or more is set, the PWM circuit 18 is prohibited from outputting a high pulse, and the switching energization operation of the switching element 4 is stopped.

  As described above, in the present embodiment, the output value of the input current detection unit 11 and the input current setting unit are set so that the input current Iin input from the AC power supply 10 is the current set by the input current setting unit 19. The on-time Ton of the on-time setting means 20 is changed according to the output value of 19, the energization control of the switching element 4 is performed at the Ton time, and the on-time (Ton) set by the on-time setting means 20 is the maximum on When the constant ON time set in the time setting means 22 is set as above, the PWM circuit 18 is prohibited from outputting a high pulse, and the switching energization operation of the switching element 4 is stopped. When the voltage decreases, the ON time set by the ON time setting means 20 of the switching element 4 increases, so the set ON time becomes the maximum ON When the ON time equal to or longer than the set ON time of the interval setting means 22 is reached, the control means determines that the AC power supply voltage has decreased to a voltage value below a certain value, and then the AC power supply voltage returns to the original rated voltage. The switching element 4 so that components such as the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5 and the diode bridge 7, the choke coil 8 and the high frequency smoothing capacitor 9 constituting the rectifying means 6 do not operate beyond the performance guarantee. Because the current supply operation is stopped, the detection circuit for detecting the voltage of the AC power supply and the power supply abnormality detection circuit for detecting the abnormal voltage of the AC power supply voltage are not required. When the power supply voltage returns to normal, the electronic components and semiconductor components used inside the rice cooker can be prevented from being destroyed, deteriorated, or shortened. .

(Embodiment 2)
FIG. 4 is a system diagram of a main part of the rice cooker according to the second embodiment of the present invention.

  4, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted because it is the same as that of the first embodiment.

  In FIG. 4, the microcomputer 17 stores in advance an 8-bit set value corresponding to a target value of a plurality of input currents Iin in an internal ROM, and sets a predetermined value for each condition such as a rice cooking process and a pan size. The input current setting means 19 for outputting a set value of 8 bits corresponding to the target value, the on-time setting means 20 for setting the switching on time of the switching element 4, and the output voltage of the input current detection means 11 to the AD converter An input value is compared with an output value of the input current setting means 19, and a control means 21 for controlling the on time of the switching means set by the on time setting means 20, and an on time set by the on time setting means 20 The on-time setting means 20 for setting the on-time of the switching circuit 4 and the PWM circuit 18 that outputs a high pulse at a constant time. And a maximum on-time change amount setting means 27 for setting the maximum value of the change amounts.

  When the ON time change amount set by the ON time setting means 20 becomes equal to or greater than the ON time change amount set by the maximum ON time change amount setting means 27, the control means 21 causes the PWM circuit 18 to output a high pulse. The switching energization operation of the switching element 4 is stopped.

  About the rice cooker comprised as mentioned above, the operation | movement and an effect | action are demonstrated below, referring FIG.

  FIG. 5 is a graph showing the relationship between the input current Iin supplied from the AC power supply 10 and the on time (Ton) set by the on time setting means 20.

  When the power supply voltage Vin of the AC power supply 10 is a constant voltage (for example, Vin = 100V), the input current Iin indicates that the input current Iin increases as the on-time (Ton) set by the on-time setting unit 20 increases. ing.

  Specifically, in order to supply 12 A of the input current Iin at the AC power supply voltage Vin = 100 V, the on time requires Ton1 (point a), and when the on time extends to Ton2, the input current Iin is 14 A ( Ascend to point b).

  Further, when the AC power supply voltage (Vin) is low, the input power (Iin) is low in the same on-time (Ton). Specifically, at the AC power supply voltage Vin = 80V, the input current (Iin) is Iin at the on time Ton1 (point a) required to supply the input current Iin of 12A with the AC power supply voltage Vin = 100V. = 10 A (point c).

  That is, in order to supply the input current (Iin) up to 12 A at the AC power supply voltage Vin = 80 V, it is necessary to extend the on-time (Ton) to Ton2 (point d).

  Here, the relationship between the on time (Ton) and the input current (Iin) when the AC power supply 10 drops from the rated voltage 100V to 80V due to a power supply abnormality and then returns to the rated voltage will be described.

  On-time setting when the target value of the input current setting means 19 is set so that the AC power supply voltage (Vin) is 100V, the rice cooker starts the rice cooking operation, and the input current (Iin) is 12A. The means 20 sets the on time (Ton) to Ton1 (point a), outputs the on time to the PWM circuit 18, and energizes the switching element 4 by the driving means 16 during the on time Ton1.

  In this state, when the AC power supply voltage (Vin) decreases to 80 V, the switching element 4 is energized at the on-time Ton1 at the time of the decrease, so the input current (Iin) decreases to 10 A (point c).

  The control means 21 detects that the input power (Iin) is lower than 12A by the output from the input current detection means 11, and the on-time of the on-time setting means 20 so that the input power (Iin) is 12A. In order to vary (Ton), the on-time is extended to Ton2 (point d). Thereafter, the switching element 4 is energized by the driving means 16 at this on time Ton2 (point d), and the input current (Iin) is operated at 12A.

  In this state, when the AC power supply voltage (Vin) returns to the original rated voltage of 100 V, the switching current 4 is energized at the on-time Ton2 at the instant when the AC power supply voltage (Vin) is restored. To rise.

  At this time, the current (Ic) and the collector voltage (Vce) are applied to the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5 so that the input current (Iin) becomes 14A.

  The control means 21 detects that the input power (Iin) has risen above 12A from the output from the input current detection means 11, and the on-time of the on-time setting means 20 so that the input power (Iin) becomes 12A. In order to vary (Ton), the ON time is shortened to Ton1 (point a).

  Thereafter, the switching element 4 is energized by the driving means 16 at the on time Ton1 (point a), and the input current (Iin) is operated at 12A.

In this way, the AC power supply 10 (Vin) becomes the rated voltage 10 because the AC power supply 10 is abnormal.
When the voltage drops from 0 V to 80 V and then returns to the rated voltage, the input current Iin rises to 14 A, although instantaneously at the time of return, with respect to the target value 12 A set by the input current setting means 19.

  In this state, components such as the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5, the diode bridge 7 constituting the rectifying means 6, the choke coil 8, and the high frequency smoothing capacitor 9 are allowed to have an allowable current (for example, Ic ) And withstand voltage (for example, collector voltage Vce).

  On the other hand, when the AC power supply voltage (Vin) of the AC power supply 10 is 110V higher than the rated voltage 100V and the rice cooker is in the rice cooking operation, the AC power supply voltage (Vin) decreases from 110V to 80V due to power failure. Then, the relationship between the on-time (Ton) and the input current (Iin) when returning to 110V will be described.

  On-time setting when the target value of the input current setting means 19 is set so that the AC power supply voltage (Vin) is 110V, the rice cooker starts the rice cooking operation, and the input current (Iin) is 12A. The means 20 sets the on time (Ton) to Ton11 (point h), outputs the on time to the PWM circuit 18, and energizes the switching element 4 by the driving means 16 during the on time Ton1.

  In this state, when the AC power supply voltage (Vin) decreases to 80 V, the switching element 4 is energized at the on-time Ton11 at the time of the decrease, so the input current (Iin) decreases to 9 A (point i).

  The control means 21 detects that the input power (Iin) is lower than 12A by the output from the input current detection means 11, and the on-time of the on-time setting means 20 so that the input power (Iin) is 12A. In order to vary (Ton), the on-time is extended to Ton2 (point d).

  Thereafter, the switching element 4 is energized by the driving means 16 at this on time Ton2 (point d), and the input current (Iin) is operated at 12A.

  In this state, when the AC power supply voltage (Vin) is restored to the original voltage 110V, the switching current 4 is energized at the on-time Ton2 (point d) at the instant of the restoration, so that the input current (Iin) is 15.4A. Ascend to (point j). At this time, the current (Ic) and the collector voltage (Vce) are applied to the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5 so that the input current (Iin) becomes 15.4A.

  The control means 21 detects that the input power (Iin) has risen above 12A from the output from the input current detection means 11, and the on-time of the on-time setting means 20 so that the input power (Iin) becomes 12A. In order to vary (Ton), the ON time is shortened to Ton11 (point h). Thereafter, the switching element 4 is energized by the driving means 16 at this on time Ton11 (point h), and the input current (Iin) is operated at 12A.

  As described above, when the AC power supply 10 has a power supply abnormality and the AC power supply voltage (Vin) decreases from the voltage 110V to 80V and then returns to the voltage 110V, the input current Iin is set by the input current setting means 19. With respect to the target value 12A, it rises to 15.4A although it is instantaneous at the time of return.

In this state, components such as the resonance capacitor 3 and the switching element 4 constituting the inverter circuit 5, the diode bridge 7 constituting the rectifying means 6, the choke coil 8, and the high frequency smoothing capacitor 9 are allowed to have an allowable current (for example, Ic ) And withstand voltage (for example, collector voltage Vce) cannot be designed.

  Specifically, since the collector voltage (Vce) withstand voltage guarantee of the switching element 4 is 1000 V, the AC power supply voltage (Vin) of the AC power supply 10 flows 12 A of the input current (Iin) when the rated voltage is 100 V. When the on-time (Ton) of the setting means 20 is Ton1 (point a) and the collector element (Vce) is applied at 750 V when the switching element 4 is switched, the on-time (Ton) of the on-time setting means 20 is Ton2 (point When the input current (Iin) flows by 14 A after extending to b), a collector voltage (Vce) of 950 V is applied.

  On the other hand, when the AC power supply voltage (Vin) of the AC power supply 10 is 110 V, the input current (Iin) flows 12 A, so that the on-time setting means 20 has an on-time (Ton) of Ton11 (point h) to switch the switching element 4. In operation, a collector voltage (Vce) of 780 V is applied.

  Furthermore, when the ON time (Ton) of the ON time setting means 20 extends to Ton2 (point j) and the input current (Iin) flows 15.4 A, the collector voltage (Vce) is applied at 1000 V, and the collector voltage ( Vce) Limiting operation with guaranteed breakdown voltage.

  That is, when the ON time (Ton) set by the ON time setting means 20 becomes longer from Ton11 to Ton2 within a certain time, it indicates that the switching element 4 may be destroyed. It is necessary to prevent the switching element 4 from performing a switching operation in the time variation (Ton2-Ton11).

  Therefore, the change amount of the ON time set in the maximum ON time change amount setting means 27 is set to a time TA shorter than the above Ton time fluctuation (Ton2-Ton11), for example, the AC power supply voltage (Vin) of the AC power supply 10. At the rated voltage of 110 V, when the on-time at which the input current (Iin) flows 14 A is Ton12 (point k), TA = (Ton2-Ton12) is set, and the control means 21 is set by the on-time setting means 20 When the change amount of the on-time becomes a change amount equal to or larger than the on-time change amount TA set in the maximum on-time change amount setting means 27, the PWM circuit 18 is prohibited from outputting a high pulse, and the switching element 4 is energized for switching. Stop operation.

  Here, the fixed time for observing the amount of change in the on-time is that the control means 21 reduces the AC power supply voltage (Vin) from 110V to 80V as described above, and the input power (Iin) is less than 12A. In order to change the on-time (Ton) of the on-time setting unit 20 so that the decrease is detected by the output from the input current detecting unit 11 and the input power (Iin) is 12 A, the on-time is set to Ton2 (point What is necessary is just to set to the time more than the control time until it extends to d).

  As described above, in the present embodiment, the output value of the input current detection unit 11 and the input current setting unit are set so that the input current Iin input from the AC power supply 10 is the current set by the input current setting unit 19. The on-time Ton of the on-time setting means 20 is changed according to the output value of 19, the energization control of the switching element 4 is performed at the Ton time, and the on-time (Ton) set by the on-time setting means 20 is the maximum on When the amount of change exceeds the ON time change amount TA set in the time change amount setting means 27, the PWM circuit 18 is prohibited from outputting a high pulse, and the switching energization operation of the switching element 4 is stopped.

  As a result, when the voltage of the AC power supply 10 decreases, the on-time set by the on-time setting unit 20 of the switching element 4 increases, so that the set on-time change amount is set in the maximum on-time change amount setting unit 27. When the on-time change amount TA is greater than or equal to the TA time, the control means determines that the AC power supply voltage has dropped to a voltage value below a certain value, and then the resonance that constitutes the inverter circuit 5 when the AC power supply voltage returns to the original voltage. Because the components such as the capacitor 3, the switching element 4, and the diode bridge 7, the choke coil 8, and the high frequency smoothing capacitor 9 constituting the rectifying means 6 are stopped, the energizing operation of the switching element 4 is stopped. Requires a detection circuit to detect the AC power supply voltage and a power supply abnormality detection circuit to detect abnormal voltage of the AC power supply voltage Without detecting an abnormal drop in the AC power supply voltage, if the AC power supply voltage returns to normal, the electronic components and semiconductor components used inside the rice cooker will be destroyed, deteriorated, or shortened. Can be prevented.

  As described above, the rice cooker according to the present invention determines that the voltage of the AC power supply is low by the on time set by the on time setting means of the switching means of the inverter, and stops the energization operation of the switching means. When the voltage drops once due to fluctuations in the voltage of the AC power supply and then returns to normal, the electronic components and semiconductor parts used inside the rice cooker are destroyed, deteriorated, or have a short life. Can be prevented and reliability can be increased, so that it can be applied not only to household use but also to rice cookers for business use, and other devices using an inverter.

DESCRIPTION OF SYMBOLS 1 Pan 2 Heating coil 4 Switching element 5 Inverter circuit 6 Rectification means 10, 35 AC power supply 11, 43 Input current detection means 19 Input current setting means 20 On time setting means 21, 52 Control means 22 Maximum on time setting means

Claims (1)

A heating coil for heating the pan; inverter means for supplying high-frequency power to the heating coil; switching means for constituting the inverter means; rectifying means for rectifying an AC power supply and supplying power to the inverter means; and the AC power supply An input current detecting means for detecting an input current supplied from the input means; an input current setting means for setting a target value of the input current; an on-time setting means for setting an on-time of the switching means; A maximum on-time change amount setting means for setting a maximum value of a change amount of time; an on-time of the on-time setting means according to an output value of the input current detection means and an output value of the input current setting means; and the switching Control means for controlling the energization operation of the means, and the control means is a constant on-time set by the on-time setting means. If the change amount is set ON hours of the variation of the maximum on-time change amount setting means in rice cooker was configured to stop the power supply operation of said switching means.

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